This invention relates to power line communication systems, and more particularly to a power line communication system that is re-configurable to adapt the utility meter to the specific utility usage and display characteristics of the attached dwelling.
Present utility meter communication devices may employ several electronic parts which result in a high cost of acquisition and maintenance of the communication hardware. It is desirable to have a simple and adaptable utility meter communications system with few parts that can communicate with other utility meters and with a central database using standard protocols.
Currently there are numerous method available for utility meters to communicate to a central location. There are wireless methods, such as those marketed by ITRON.TM., CELLNET.TM., and standard protocols that operate in the 900 MHz ISM band. There are methods utilizing Power Line Carrier (PLC) techniques, such as those marketed by INTELLON.TM.. Other methods include the use of integrated telephone modems. Additionally, communication modalities include optical communications, such as industry standard Infrared Data Association (IRDA), or direct communication with an external device via a serial port. In yet another communicating mode, one utility meter may function as a "bridge" for communications between other utility meters and a central hub, or to pass information in a daisy-chain manner through meters and eventually to a hub. It is desirable to have a utility meter that can be easily adapted to communicate using a variety of communication methods and protocols.
In electronic utility metering applications, conflicting demands exist for flexibility of metering functions and a low cost electronics metering platform. It is desirable to have a utility meter that uses "soft-key" to select measurement, calibration, and display features of the utility meter.
While LCD (Liquid Crystal Display) driver integrated circuits are readily available from many commercial sources, they are costly for high volume applications which have simple display requirements, such as electric meters. Typical LCD driver implementations use analog circuits to develop the multiple voltage levels required to drive multiplexed LCDs. Some implementations use voltage references and voltage multipliers to produce the required voltages which are coupled onto the LCD driver lines as required. Other drivers use resistive dividers to produce voltages necessary to drive the LCD segments. Resistive dividers require external parts and consume additional power. It is desirable to have a low cost and low power LCD driver which utilizes a microprocessor to drive the LCD display.
High volume electric meters, such as residential electric meters, are typically designed with cost economy as a primary goal--a large contributor to the cost of such a meter is the power supply. Thus, it is important to design the meter optimizing the cost of the power supply. When power is removed from the typical utility meter it is important that the meter power supply contain enough stored energy to allow the meter to continue to function for a short time (i.e., .apprxeq.100 ms) so as to store important information, such as accumulated kilowatt-hours, in non-volatile memory. The alternative is to simply lose all information stored in volatile memory when power is lost. Providing an appropriate power-off sequence for the meter can reduce the energy requirement of the power supply, saving cost in the meter while still allowing important information to be saved.
In a typical solid state electric meter many functions of the meter such as metering algorithms, time-keeping, display, communications, etc., are controlled by a central processor. Each of these functions has a varying degree of importance in the event of a power failure. It is desirable to have a utility meter with an appropriately sized power supply to enable the utility meter to recover from a loss of power in a predictable manner.
In cost sensitive applications such as residential electricity meters, typical assembly techniques which include wires and soldered electrical connectors add unnecessary cost to the electric meter. A typical assembly technique includes soldering to the voltage bus-bar wires with relatively expensive connectors which are then attached to the printed wiring board (PWB) during assembly. It is desirable to have a utility meter that can be quickly and easy assembled without the use of soldered connections, screws, and wire bundles.
Traditionally, an iterative approach has been used in the calibration of residential electromechanical and electronic electricity meters, requiring a high accuracy meter standard, a single-bit test output signal, and multiple calibration cycles or multiple calibration stations under various test conditions. Traditionally, the test setup uses fixed currents at 3 Amps, and 30 Amps for these calibration points as required by the utility industry. These procedures require a count of the number of transitions of the single-bit test output signal over a fixed period of time to calibration the meter. It is desirable to employ a utility meter that can be quickly calibrated and accurately calibrated without having to count the number of transitions of a single-bit output signal.